Area Code Atlas

NANP- Introduction of New 671 (Guam) Numbering Plan Area (NPA)

NPA 671 introduced for Guam

Area code 671 was introduced for Guam on July 1, 1997, replacing the island's previous international country code and integrating Guam into the North American Numbering Plan. This change allowed calls between Guam and the U.S. mainland to be dialed as domestic calls.

Permissive dialing period begins for NPA 671

Permissive dialing for area code 671 began on July 1, 1997, allowing both the new area code and the previous international dialing method to be used for calls to Guam during the transition.

Mandatory dialing of NPA 671 begins

Mandatory dialing of area code 671 began on July 1, 1998, ending the permissive period and requiring all calls to Guam to use the new area code format.

Area code 671 activated for mandatory dialing

Area code 671 became mandatory on July 1, 1998, ending the permissive dialing period. Callers from the U.S. and Canada were required to dial 1-671 plus the seven-digit number to reach Guam.

National toll-free numbers become accessible from Guam

National toll-free numbers, including area codes 800, 888, 877, 866, 855, and 844, became accessible to callers from Guam in April 2015. This expansion allowed residents to use U.S. toll-free services, which became popular with the rise of prepaid phone cards.

NPA 671 transitioned to ten-digit dialing due to 988 Lifeline implementation

Area code 671 was transitioned to ten-digit dialing on October 24, 2021, due to the nationwide designation of 988 as the three-digit code for the National Suicide Prevention Lifeline. This change was required to resolve conflicts with existing seven-digit dialing for numbers using the 988 central office code.